Heretofore, this sport of the `ink jet printer` device is such a printer device in which ink drops are emitted responsive to a recording signal for printing a picture on a recording medium, such as paper of film. Recently, this sort of the printer device is finding extensive application because it can realize a small size and a low cost.
In this `ink jet printer` device, two methods, for example, are used for emitting ink drops, namely a method of employing heating elements and a method of using piezoelectric devices, such as piezo devices.
With the method of employing the heating elements, ink drops are emitted via an emission nozzle under the pressure of bubbles generated on heating the ink to ebullition by the heating elements.
With the method of using the piezoelectric devices, the piezoelectric devices are deformed for pressurizing a pressure chamber charged with the ink for emitting the ink liquid drops via a nozzle port communicating with the pressurizing chamber and via an emission nozzle.
Among the methods of using the piezoelectric devices, there are a method of linearly displacing a layered type piezoelectric device comprised of three or more piezoelectric portions bonded to a vibrating plate for pressurizing the pressure chamber via the vibrating plate and a method of applying a voltage across single-layer or two-layer piezoelectric portions bonded to a vibrating plate for pressurizing the pressure chamber via the vibrating plate.
FIG. 119 shows an illustrative structure of a printer head in this sort of the `ink jet printer` device. This printer head 10200 includes a first solution supply duct 10202 formed for opening on a surface 10201a of a base block 10201 and flown through by an ink supplied from an ink tank, not shown, a pressurizing chamber 10203 formed for opening on the surface 10201a of the base block 10201 in communication with the first solution supply duct 10202 and a second solution supply duct 10204 formed on the opposite side with respect to the first solution supply duct 10202 on both sides of the pressurizing chamber 10203 towards the surface 10201a of the base block 10201.
The base block 10201 is formed with a nozzle inlet port 10205 for opening on an opposite side surface 10201b of the base block 10201 in communication with the second solution supply duct 10204. On the surface 10201a of the base block 10201 is bonded a vibration plate 10206 via an adhesive, not shown. The vibration plate 10206 covers the ports in the pressurizing chamber 10203 and the first and second solution supply ducts 10202, 10204. To the vibration plate 10206 is mounted an ink supply pipe, not shown, connected to the ink tank. To this end, the vibration plate 10206 is formed with a through-hole, not shown, conforming to the ink supply pipe.
On a surface 10206a of the vibration plate 10206 in register with the pressurizing chamber 10203 is bonded a single-plate type piezoelectric device 10207 by an adhesive, not shown.
On the opposite side surface 10201b of the base block 10201 is bonded an orifice plate 10208 by heat pressing for covering the opening area of the nozzle inlet port 10205. In this orifice plate 10208 is bored an emission nozzle 10208a in communication with the nozzle inlet port 10205.
If a pre-set pressure is applied on the piezoelectric device 10207 of the printer head 10200, this piezoelectric device 10207 becomes contracted in the in-plane direction by the bimorph effect so as to be warped in a direction shown by arrow A in FIG. 119. With such warping of the piezoelectric device 10207, the vibrating plate 10207 is warped in the direction shown by arrow A in FIG. 119. The result is that the pressurizing chamber 10203 is decreased in volume and hence increased in pressure so that the ink charged into the pressurizing chamber 10203 is discharged via emission nozzle 10208a through the nozzle inlet port 10205.
In the above-described printer head, plural pressurizing chambers 10203 are arranged side-by-side. The first solution supply ducts 10202 are arrayed in parallel with the longitudinal direction of a connection pipe with an ink tank, not shown, termed an ink buffer tank 10209. It should be noted that the first solution supply ducts 10202 are arranged in a direction perpendicular to the arraying direction of the pressurizing chambers 10203, that is at right angles with a supply surface 10209a of the ink buffer tank 10209 (the connection surface of the first solution supply duct 10202 in the ink buffer tank 10209). The ink is supplied from the ink tank via an ink supply pipe, not shown, mounted in a through-hole 10209b of the ink buffer tank 10209. Thus, the ink supplied from the ink tank via the ink buffer tank 10209 is supplied to the second solution supply duct 10204.
Recently, document preparation using a computer, termed desktop publishing, has become popular, such that a demand for outputting not only letters or figures but also a colored natural image such as a photograph along with the letters or figures is increasing. For printing the natural image of high quality, reproduction of the half the is crucial.
For representing the half tone, the voltage or the pulse width applied to the piezoelectric device or heating device is changed for controlling the emitted liquid drop size for varying the represented printing dot diameter. Alternatively, each pixel is constituted by a matrix of, for example, 4x4 dots, without changing the dot diameter, for representing the gradation by the so-called dither method on the matrix basis.
However, with the method of controlling the emitted liquid drop size in the printer head of the `ink jet printer` device by varying the voltage or pulse width applied to the piezoelectric device or heating device, there is imposed a limitation to the minimum liquid drop size because the ink cannot be emitted if the voltage or the pulse width applied to the piezoelectric device or heating device is lowered excessively. The result is that the low concentration, in particular, cannot be represented such that the number of gradations that can be represented becomes smaller.
On the other hand, if each pixel is represented by a 4.times.4 matrix by the method of representing the gradation by the dither method, 17 gradations of the concentration can be represented, however, if printing is done with the same dot density as that in the above method, deterioration is lowered by one-fourth to render roughness apparent. Thus, none of the above methods is practically not sufficient to print out a natural image.
For eliminating the defect of the `ink jet printer` device, there has recently been proposed a `carrier jet printer`. The printer head of the `carrier jet printer` device gives gradation in a dot by a quantitation nozzle for quantitating an ink and emitting the resultant quantitated ink and an emission nozzle for emitting the dilution solution. The ink emitted by the quantitation nozzle and the dilution solution emitted by the emitting nozzle are unified for varying the ink concentration for giving the gradation in a dot.
This `carrier jet printer` device also is in need of an ink drop emitting function similar to that required of the `ink jet printer` device. As a method for emitting the drops, a method of employing a piezoelectric device or a heating device similar to that used in the `ink jet printer` device is customarily used.
The printer head of the above-mentioned `carrier jet printer` device is constructed as follows: On one surface of the base block, there are defined a first pressurizing chamber charged with a dilution solution, a second pressurizing chamber charged with ink and first and second liquid supply ducts for supplying the dilution liquid and the ink thereto. On one surface of the base block is bonded a vibration plate by an adhesive. A piezoelectric device for impressing a pressure to the first pressurizing chamber is provided on a portion of the vibration plate in register with the first pressurizing chamber, whilst a piezoelectric device for impressing a pressure to the second pressurizing chamber is provided on a portion of the vibration plate in register with the second pressurizing chamber.
On the opposite surface of the base block are formed first and second nozzle inlet ports communicating with the first and second pressurizing chambers, respectively, and an orifice plate formed with an emission nozzle and a quantitation nozzle communicating with the first and second nozzle inlet ports, respectively.
The first and second liquid supply ducts communicate with a dilution liquid buffer tank and an ink buffer tank, respectively. The first and second liquid supply ducts are arrayed at right angles with the arraying direction of the first and second pressurizing chambers, that is with the supply surface of the dilution liquid buffer tank and the delivery surface of the dilution liquid buffer tank, as in the case of the above-mentioned printer head 1.
In the through-holes of the ink buffer tank and the dilution liquid buffer tank are mounted an ink supply pipe connected to the ink tank and a dilution liquid supply pipe connected to the dilution liquid tank. Thus, the ink supplied form the ink tank via an ink buffer tank is supplied to the second liquid supply duct, while the dilution liquid supplied from the dilution liquid tank via dilution liquid buffer tank is supplied to the first liquid supply duct.
In the above example, the dilution liquid is used as the quantitation medium, whilst the ink is used as a quantitation medium. Alternatively, the ink and the dilution liquid may be used as the emitting medium and the quantitation medium, respectively.
Meanwhile, in the `ink jet printer` device and `carrier jet printer`, it is required of the printer head to deposit the emitted liquid accurately on a recording medium, such as a paper sheet. In particular, if characters, such as letters, and natural images, are regenerated with high definition on a recording medium, the dot size on such recording medium is required to be as small as at most 200 .mu.m or less. Thus, an emission nozzle having a diameter at most 100 .mu.m or less and preferably on the order of 30 to 50 .mu.m and an aspect ratio of 1 or larger needs to be formed on an orifice plate, thus requiring high processing precision.
If a drill is used as means for processing the emission nozzle, the above-mentioned condition cannot be met without difficulties, because a limitation is imposed on the processing diameter. For enabling processing of the emission nozzle for satisfying the above conditions, it has recently been frequently tried to perforate a through-hole for an emission nozzle in an orifice plate using laser, such as eximer laser.
That is, if a through-hole for an emission nozzle s formed in an orifice plate of an organic material, such as polyimide or polysulfide, the through-hole can be formed efficiently because of the large depth of the hole that can be processed per pulse. However, if a through-hole for an emission nozzle is formed in an orifice plate of a metal material, such as stainless steel, the through-hole can be formed only with poor efficiency as compared to the case of forming the through-hole for a nozzle in the orifice plate of an organic material because of the depth of the through-hole per pulse shallower than that of the hole for the organic material. Moreover, the through-hole thus formed is not suited to an emission nozzle such that the printer device is lowered in productivity and performance.
For efficiently emitting the liquid drops in the `ink jet printer` device or in the "carrier jet printer" device, in other words, for assuring reliability of the printer device, the pressure generated by the piezoelectric device needs to be impressed effectively to the first or second pressurizing chambers charged with the dilution liquid or the ink. Thus, the orifice plate needs to be formed of metal, such as stainless steel, higher in strength than the organic material and having a thickness on the order of, for example, 90 .mu.m. In particular, if a piezoelectric device is used as pressure impressing means for impressing the pressure to the first and second pressurizing chambers, the pressurizing chambers need to be larger in size than if the heating device is used, so that a higher strength is required of the material of the wall member of the pressurizing chambers.
Thus, if a piezoelectric device is used as pressurizing means for pressing a pressure to the first and second pressurizing chambers, the orifice plate needs to be formed of a material, such as stainless steel, with a strength and a thickness large enough to apply an effective pressure against the first and second pressurizing chambers. However, if the orifice plate is formed of for example, stainless steel, laser characteristics cannot be fully displayed, as discussed previously.
That is, such orifice plate capable of sufficiently meeting the requirements for a strength necessary for effectively and stably increasing the pressure within the first and second pressurizing chambers and processing amenability to laser cannot be realized without difficulties.
In such printer device, it has been required to enable the pressure within the pressurizing chamber effectively and stably, to sufficiently meet processing amenability to laser, to form an emission nozzle to high precision and to improve productivity and reliability.
Meanwhile, in the above-described `ink jet printer` and `carrier jet printer`, it is necessary for the ink or the dilution solution to be charged without forming air bubbles in the pressurizing chamber. This pressurizing chamber is the pressurizing chamber in the case of the `ink jet printer` and the first and second pressurizing chambers in the case of the `carrier jet printer`. Thus, a highly advanced bonding technique is required for bonding to a base block a vibration plate arranged for overlying these pressurizing chambers.
Among the methods of bonding the vibration plate to the base block, there is a method consisting in applying an adhesive to an adhesive surface of the vibration plate and subsequently bonding the vibration plate to the base block. However, in this case, it is technically difficult to set the thickness of the adhesive layer applied to the vibration plate to not more than 2 .mu.m, such that, if the liquid supply duct (liquid supply duct in the case of the `ink jet printer` and first and second liquid supply ducts in the case of the `carrier jet printer`) formed in the base block is of shallow depth, these liquid supply ducts tend to be stopped with the adhesive. If the liquid supply ducts are stopped in this manner, the resistance by the liquid supply duct is increased, so that the printer device tends to be lowered in reliability.
Among the methods of eliminating these problems, there is a method of increasing the aspect ratio of these liquid supply ducts for preventing the liquid supply ducts from being stopped by the adhesive. The liquid supply duct with a high aspect ratio can be formed by anisotropic etching using, for example, a silicon substrate as the base block.
However, in this case, an inconvenience is raised that the freedom in selecting the material type of the vibration plate is limited significantly. It is because the vibration plate is heated and pressured in bonding the vibration plate to the base block and hence the thermal expansion coefficient of the vibration plate needs to be approached to that of the silicon substrate.
There has also been proposed a method of bonding the vibration plate to the base block using a thermoplastic adhesive sheet for preventing the liquid supply duct from being stopped with the adhesive (Japanese Patent Application 5-183625). However, in this case, since the adhesive sheet is bonded by pressuring under heat application, it is necessary to form a bore in meeting with a through-hole previously formed in the vibration plate for attaching the ink supply duct to the vibration plate, thus correspondingly increasing the bonding steps.
In addition, since the bore needs to be formed in the adhesive sheet in consideration of the contraction ratio thereof, an extemely high degree of precision is required in registration between the bore in the adhesive sheet and the through-hole in the vibration plate. Moreover, a high degree of precision is required in temperature management during pressure bonding under heat application, thus complicating the bonding step for the vibration plate.
Thus, a method of bonding the vibration plate to the base block without using the adhesive, has also been proposed, such as a method of bonding the vibration plate to the base block using a dry film resist exhibiting photosensitivity and adhesive properties.
However, with the method of using a dry film resist, thermosetting processing is required for rendering the dry film resist in use resistant against the ink and the dilution solution thus correspondingly increasing the number of steps and complicating the bonding process. Also, since the light exposure device is required, the production cost for the printer head is raised or the production process is complicated.
There is also known a method of bonding the vibration plate to the base block by anodic bonding using a vitreous material as the material for the base block and the vibration plate, as a method of bonding the vibration plate to the base without using an adhesive. In this case, since the vitreous material is weak against impact or damage, it is difficult to select the thickness of the vibration plate to not more than 10 .mu.m for maintaining a pre-set strength. The result is that it becomes difficult to reduce the driving voltage applied to the piezoelectric device thus raising the load applied to the piezoelectric device while increasing the power consumption of the printer device. Also, it becomes difficult to reduce the size of the pressurizing chamber, that is to reduce the pitch of the emitting nozzles and/or the quantitating nozzles.
Thus, in the prior art device, the liquid supply duct is stopped by the adhesive if such adhesive is used for bonding the vibration plate, thus lowering the reliability of the printer device, whereas, if the adhesive is not used for evading the stopping of the liquid supply duct by the adhesive, the bonding process becomes complicated.
Thus, in the printer device, it is a desideratum that the vibration plate be bonded to the base block with high precision to improve reliability without complicating the bonding process for the vibration plate.
Meanwhile, if air bubbles exist in the pressurizing chamber n the above-described printer head of the `ink jet printer` or of the "carrier jet printer", the air bubbles present in the pressurizing chamber are merely reduced in volume under pressure if the pressure in the pressurizing chamber is increased by pressurizing means, such as piezoelectric device provided in the pressurizing chamber, while the liquid charged in the pressurizing chamber is not increased in pressure. That is, the air bubbles, as a compressible fluid, absorb the pressure applied by the pressure increasing means, thus extruding the ink via the quantitation nozzle to render it difficult to emit the dilution liquid mixed with the ink (mixed liquid drops) via emission nozzle. Moreover, the ink or the mixed liquid drops emitted via the emission nozzle become insufficient in volume or velocity thus deteriorating the picture quality.
Therefore, in both the printer head of the `ink jet printer` and the printer head of the `carrier jet printer`, it has been crucial to eliminate air bubbles left in the pressurizing chamber.
In order for air bubbles not to be present in the pressurizing chamber, it is crucial that air bubbles be not allowed to enter the inside of the pressurizing chamber at the time of tank mounting such as when the printer device is started to be used or when the ink tank or the dilution liquid tank is exchanged. It is also crucial that air bubbles be not allowed to enter the inside of the pressurizing chamber during printing.
However, as for the air bubbles mixed during mounting of the solution tank, there are occasions wherein no liquid is present on the wall surface of the pressurizing chamber, such that, as shown in FIGS. 121 and 122, there is the possibility that the air bubbles be affixed to the wall surface of the pressurizing chamber 10210 or to the wall surface of the nozzle inlet hole 10211,. The air bubbles, once affixed to the wall surface of the pressurizing chamber 10210 or to the wall surface of the nozzle inlet hole 10211, cannot be discharged by usual maintenance out of the pressurizing chamber 10210 or the nozzle inlet hole 10211. In particular, if, with air bubbles 10213, shown in FIGS. 121 and 122, present in the pressurizing chamber 10210 or the nozzle inlet hole 10211, the liquid is charged into emission nozzle 10212, such that the liquid meniscus has been formed in the vicinity of the foremost part of the emission nozzle 10212, it is difficult to remove the air bubbles present in the pressurizing chamber 10210 or the nozzle inlet hole 10211.
Thus, in the printer device, t has been a desired to reduce the amount of air bubbles affixed to the wall surface of the pressurizing chamber more extensively than in the conventional system, in particular, to reduce the amount of air bubbles affixed to the wall surface of the pressurizing chamber during mounting the ink tan and/or dilution liquid tank to improve the picture quality of the recorded picture to improve the reliability of the device.
Meanwhile, in the above-mentioned `ink jet printer's or `carrier jet printer`, it has been desired to reduce the device size. However, if, in these printers, the silicon substrate is used as the base block, and a liquid supply duct with a high aspect ratio is to be formed by anisotropic etching, with a view to preventing the liquid supply duct from being stopped by the adhesive as discussed previously, the direction of forming the liquid supply duct cannot be selected freely, because it is not possible with anisotropic etching to select the crystal plane freely. The result is that the liquid supply duct can be formed only in a direction perpendicular to the arraying direction of the pressurizing chambers, resulting in increased area of the liquid supply duct with respect to the overall printer head and increased difficulties in coping with reduction in size of the printer device.
Thus, in the above printers, it is an incumbent task to reduce an area taken up by the liquid supply duct to meet the demand for size reduction.